Telephone-exchange system.



. S. CONNER.

TELEPHONE EXCHANGE SYSTEMi APPLICATION FILED JAlms, 1907.

Patented ct.20,1908.

Z SHEETS-SHEET l.

ms :vonnis rsrsns co., wnsumcrow, p-c4 M. S. GONNER.

TELEPHONE EXCHANGE SYSTEM,

APPLICATION FILED JAN.23, 1907.

Patented Oct. 20, 1908. 2 SHBETS-SHEBT 2.

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MERRITT S. CONNER, OF ROCHESTER, NEW YORK, ASSIGNOR TO STROMBERG-CARLSON TELE- PHONE MANUFACTURING COMPANY, OF ROCHESTER, NEW YORK, A CORPORATION OF NEW YORK.

Application filed January 23, 1907.

Specification of Letters Patent.

TELEPHONE-EXCHANGE SYSTEMI.

Patented Oct. 20, 1908.

Serial No. 353,690.

is a full, clear, concise, and exact description, reference being had to the accompanying drawings, forming a part of this specification.

My invention relates to telephone exchange systems, more particularly to improved automatic selective ringing arrangements therein, and its object is to provide an exchange system with a ringing equipment which may be maintained at a minimum ex.- pense, and which is of greater reliability and eliiciency than ringing arrangements of the prior art.

Broadly the invention provides a ringing arrangement, wherein the ringing current source, which may be of considerably less power than those which were employed in ringing equipments of the prior art, is kept constantly loaded so that instead of employing a ringing current generator of great power as in prior systems, where at one period a large demand might be made upon the machine, and at another no demand be made thereon, a generator of smaller power is employed and is so arranged that there is constantly a steady load thereon, whereby the various advantages herein pointed out are secured.

rPhis invention may be considered as an improvement over, and is particularly adaptable in connection with such telephone systems as disclosed in the copending application of Arthur R. Kahl, Serial No. 298,741,

filed January 31, 1906. On the system disclosed in this Kahl application, means are provided whereby any one of the signaling current generators, which diifer from each other in pulsations per second, could be connected with the telephone line. In this system however the ringing equipment was such that there might be a very large number of substation bells simultaneously in operation, and another time there might be a very small or practically no demand upon the ringing current. generator'. In order therefore to maintain the proper operation of such a system, the ringing current generators employed were necessarily of large power, so that they would be able to meet the large demand which might be placed upon them. The present invention however eliminates this necessity, and provides means whereby a limited number of bells may be rung simultaneously, all the other bells connected with the exchange at that time remaining inert. Thus the bell of the subscriber who is being signaled would be active for a definite period, and would remain inactive while the bells of certain other subscribers being .signaled are active. To this end the circuits are arranged in groups,

which for convenience in this description may be termed ringing divisions, each division being provided with its own selective keys and interrupters.

lieans are provided in this invention whereby several ringing divisions are brought into such relation with each other, that ringing current will be supplied to one ringing division ata time; that is, the ringing period of one division follows that of another division and is immediately succeeded bv the ringing period of another division. ihe signal current is thus fed to the circuit divisions in regular consecutive order, the maximum demand at any one time being that made by all the circuits in a single division. The maximum 'demand at any one time is thereby greatly reduced and generators of smaller power may therefore, be employed.

These various improved relations and arrangements of my invention whereby an eilicientpower automatic selective signaling system is obtained, will be 'best understood by reference to the accompanying drawings 1n which Figure 1 diagrammatically illustrates a system arranged according to my invention, and Fig. 2 illustrates diagrammatically the arrangement whereby the different signaling currents are supplied to the circuits, the collateral apparatus, however, being omitted for the purpose of clearness.

In Fig. l I have illustrated a sub-station A connected by line limbs c and b with the central exchange C, these line limbs being continuous normally through armatures 1 and 2 of the cut-off relay 3 and including the windings 4 and 5 of the indicator relay 6, connecting them with the terminals of the common source of current S. At the substation is provided the usual telephonie apparatus comprising a switchhook 7, receiver 8, transmitter 9, signal bells 10, and condenser 1l. rlllie multiple spring` acks l2 and 13 are connected iii bridge of the line limbs, and the test thiinbles i4 and l5 tliercoi are connected together by conductor 'lo which includes the cut-oli' relay 3 and terminates at the positive pole ot the battery S. line signal. 17 is included in a local circuit controlledby the armature 18 ot' the indicator relay 6. A sub-station Bl is provided with similar apparatus as sub-station A and connects through the line limbs with the central exchange C, the cut-ottI relay mechanism. and connections therefor, being the saine as those connected with the sub-station A. The reterence characters ot the sub-station B1 telephone apparatus, line and central station apparatus are, however, primed. This line is shown as a party line, and besides the substation B1 are indicated the sub-stations B2, B3 and Bt.

The cord circuit at the central exchange terminates in the answering plug lf) and the calling plug 20. Condensers 2l and 22 are included in the strands ot the cord circuit respectively to prevent their conductivity between the answering and calling sides thereof. The supervisory relay tor the answering side is otl the compound type, comprising windings 28 and 24. rlhe armature 25 tor the winding 24 is mechanically connected with the sprino 2G which tends to hold this armature in its unattracted position. Armature 27 is provided for the winding 23 and is mechanically connected with the actuating spring 28 by ineans of the insulating piece 29. Armature 25 is adapted to mechanically engage the armature 27, and the actuating spring 28 has associated therewith a contact spring 30 from which it is normally disengaged, but which it is adapted to engage when the winding 24 is energized whereby the armature 25 is attracted against the tension of the spring 26, thus allowing the armature 27 to drop, and causing the actuating.

spring 28 to engage the contact spring 30. The contact springs 28 and 30 control a circuit containing the supervisory lamp 31 and the source ot current. The supervisory relay tor the calling side comprises the windings 32 and 33. The armature 34 for the winding 33 is mechanically connected with t-he spring 35 which tends to hold it in its uiiattracted position. Mechanically connected with the armature 34 by means of the insulating piece 3G is the actuating spring 37 which has the alternate contacts 38 and 39, the purpose ot which will be hereinafter pointed out. The armature 34 by reason of the tension ot the spring 35 is adapted to engage the armature 40 tor the winding 32 whereby the actuating spring 4l by reason of its mechanical engagement with the armature 40 may be held normally out ot engagement with the contact spring 42. The actuating spring vl-l.. however, is adapted to engage the contact spring 42 when the winding 33 is energized to :it-v tract the armature against the tension ot the spring 35, thus allowing the armature 4() to drop and the actuating spring 4lY to engage the contact spring 42 ilTlir-n the windiii 33 is thus energized, the actuating spring 3l' is adapted to engage the spring JS). and when it is not energia/led, the actuating spring 37 engages the contact spring 38 by reason ot the tension oit the spring The contact-i 4l and 42 control a local circuit through the supervisory lainp 43 for the calling side and the common source oit current.

The connection with the line ot the operators telephonie apparatus O is controlled by the position oit the key springs 44 and 45. These key springs 44 and 45 are adapted upon actuation to engage respectively the contact springs 4G and 47 which are directly connected with the operators telephonie apparatus. For the purpose ot facilitating the proper description the operation ol these arraiigeii'ients is explained in regard to a single cord circuit, but as will be liei'ei. zitter pointed out, when the ringing arrangements are explained. this cord circuit should be considered as a group ot' cord circuits which are supplied in parallel with the proper ringing current. lVhile these ringing divisions herciiiliieiorc mentioned may be oli' any reasonable number, l have for the purgose ot illustration shown siX divisions, these divisions being designated conveniently as (Z, c, f, g, 7i., and c' respectively. Tt must be remembered that each of the divisions coinprises a group oi cord circuits, the number ot such groups determining, according to this invention as will be hereinatter described, the relative lengths of the active and silent periods of the signaling devices at the substations. For the purposes ot illustration and description siX groups or divisions are shown. Thus in signaling signaling device would be ot the time and silent iive-sixths.

active one-sixth ltlacli ot the groups ot cord circuits is provided with selective automatic ringing apparatus including the keys 481, 4.82, 483, andv 481.

In order that the drawings may not be too complicated, l have omitted in Fig. l the groups of cord circuits which are connected respectively with the keys 481, 482, etc. ot the ringing divisions c, f, g, 7L, and z', and il will describe the operation of the system ot' lig. l with reference to the selective keys ot group CZ alone. Each of the keys 48, 482, 48. and 48 consists of the actuating springs 4S) and 5() and the contact springs 5l and 52 adapted to be engaged by the actuating spi-ings 49 and 50 respectively. The actuating springs 50 of all the keys 48], 4.82, 481k and 48"l are connected together and to the liront contact 53 ot' the relay 54 which contact is adapted to be engaged by the armature 5.5 when the winding 5.6 of the; relay 5.4 is energized.. The relay 54 is provided also with the contact armature 5T which has the front contact 5.8, this front contact being connected with one pole of the signaling current generators by means of the conductor The actuating )ring 52 which makes the contact with the actuating spring 50 is connected with the other pole of the signal'- ing current generators through the associated interrupting devices, as will be hereinafter described. The armatures 55 and 57 are connected with the strands of the cord circuit, and it will appear evident that when the relay 54 is energized, these armatures f will be attracted to canse the signaling cur-- rent to be bridged across the cord strands.

As will be hereinafter pointed out, each of the keys of the selective apparatus of any cord circuit O'roup is adapted to send current over the line which has dierent characteristics from any of the currents which are sent over the line by the actuation of any of the other keys of the selective apparatus for that particular group. In orde-r that the currentsource may be connected with the line until the called subscriber has answered his call, I provide automatic means whereby any particular key when depressed will be retained in such depressed position by means of the energization of a relay and further means is provided whereby the circuit through this locking relay is controlled by the position of the switchhook at the called station. Thus, when the called subscriber removes his receiver from the switchhook, this loc-king relay is denergized to cause the release of the selective key, and the signaling current is, therefore automatically disconnected from the line when the subscriber has answered his call. This locking relay is designated at in Fig. l, and one terminal of its winding 61 is connected with the actuating springs 49, 49, while the other terminal thereof is connected with the negative pole of the battery. The springs 49 are adapted to engage respectively their associated contacts 51 which are connected together and with the spring 4l of the supervisory relay. The contact 42 associated with the spring 41, as before stated, is connected with the positive pole of the battery. The relay 60, therefore, is adapted to be energized upon contact between springs 49 and 51 and simultaneous contact of springs 41 and 42. Means are provided whereby con-V tacts 4I and 42 are closed together upon the insertion of the calling plug in the jack, and the depression of any selective key when the calling plugV is in the jack will cause contact between the springs 49 and 5l and will there.-

by close the circuit through the relay 60 to energize the same, thus locking the depressed whereby the springs 41 and 42 are parted upon the ie1n .val of the receiver from the hook at the called sub-station, and the circuit through the relay 60 is thus broken to denergize the same and allow the selective key to return to its normal position.

The mechanical arrangements and the precise construction of the selective apparatus are shown in detail in the co-pending application of Kahl referred to, and I, therefore,

1 here simply describe the operation of this key mechanism with reference to the diagram in a. general way, as it will appear evident that any kind of electromagnetic lock- 5 ing and releasing means may be employed.

It appears evident that the signaling current can be supplied to the line only when the relay is energized, and as will appear evident from the foregoing, signaling current should be sent over the line only when the relay' 60 is energized.. I, therefore, provide an armature which has the front contact 63 and which primarily controls the circuit through the relay 54. This circuit through the relay 54 is secondarily controlled by means ofthe int errnpter (W. 'lhe constant contact 65 of this inte-rrupter is connected to the positive pole of the battery, and the brush contacts c 6, e6, j, etc. are connected respectively with the similar relays of their associated cord circuit groups. Thus, the brush contact d6 is connected to all the relays 514 in group ZL The interrupter c6, therefore, controls the relay 54 after the relay 60l has been energized. The active period of the interrupter c6* begins immediately upon the close of the active period of the interruptor d, and the active period of the interupter f* begins immediately upon the cessation of the active period of the interrupter cjt, etc. Since, as in the present instance, there are six interrupters, one for each cord circuit group, there are six ringing periods of equal duration to take place, each immediately after the cessation of the preceding one. Therefore, the complete cycle represented by the sum of the ringing periods of all the different divisions would be represented by one revolution of one interrupter. Thus, the relays 54 of group e may become energized immediately after the relays 5.4 of group CZ have become denergia-ed.

The ringing circuit which is bridged across the cord strands whereby the current may be sent over the lines includes the current generator 67 which is one ofthe set G71, 672, 673, and GT4, the interrupter- 68 which is one of the interrupters d68, 6.68', fus, gGS, etc., and one of' the pairs of springs 50 and 52 of either the keys 48.1, 482, 483 or 484. The interrupters 68 and the interrupters 64 may be mounted on a common shaft. The generators 67 deliver currents which differ from key in position.. Means are also provided one another in pulsations per second,'and

each ot the sub-station bells on the telephone line are adapted to respond only to currents troni one ot said generators. The selective keys 481, 482, etc. are, therefore, adapted to connect any one of the generators G71, 672, GT3, etc. with the telephone line whereby a particular signal bell on that line is actuated.

.l provide means whereby the current delivered from generator' G71 is adapted to be connected with all the selective keys 481, and l' also provide means whereby this current from the generator 671 may be tir-st connected with the key 481, next with the key e481, then with key M81, etc. Similarly l provide means whereby the current delivered iroin the generator' G72 is adapted to he connected with any of the keys d8?, and also means are provided whereby this current may be fed iirst to key {Z4-82, then to key @482, then to key H82, etc. Similarly the same may be said of the groups 483 and 484. rlhis arrangement is most clearly shown in Fig. 2 where the ringing means alone have been diagrammatically shown.

The various groups oit cord circuits are in dicated at CZ, c, f, g, 7L, and z', and there is shown in this ligure only the ringing arrangements which are adapted to be bridged across the cord circuits in the respective groups. The similar poles ot the generators G71, 672, G73 and G7* are connected together and are shown as leading to the various groups of cord circuits. rhe interrupters are shown as being disposed in groups d, e, f, g, 7L, and c' corresponding with the cord circuits. As shown, the other conductor leading from each group of cord circuits is connected with all the interrupter brush contacts in the corresponding interrupter group. The interrupters are also arranged in groups l., 2, 3 and 4. All the constant contacts in group l are connected with the other pole of generator G71; all the constant contacts in group 2 are connected with the other pole ot generator' GT2, all the constant contacts in group f5 are connected with the other pole oit generator GTI", and all Vthe constant contacts in group et are connected with the other pole ot.' generator 67". lt will be convenient in this description to characterize the reference characters given the parts as to cord circuit groups by the letter indicating the cord circuit group and to give the reference characters exponents corresponding with the exponents of the `generator characters to distinguish them in the generator groups. Each of the interrupters G8 consists of the active portion G9 and the inactive portion 70, that is, inactive with regard to Fig. 2 where the collateral arrangements are omitted. The function of the portion 70, however, will be explained with reif'- crence to Fig. l.

,lt will be noted that Vthe positions of the active portions (39 which may be called the ringing segments, are the same in each cord circuit group. Since for the. purpose o'l illustration have herein shown six groups oi" cord circuits, the ringing segment ot each group is one-sixth ot' a revolution in ad vance of the ringing segment of the succeeding group. These ringing segments are equal, and when the contact brush has leit't the ringing segment of the last interrupter, the contact brush of the irst interrupter will thereupon immediately engage its ringing segment. lfilhen the contact brush has lett the ringing segment of the iirst interrupter, the brush of the second interrupter will cngage its ringing segment, and immediatelyY upon leaving its ringing segment, the brush ot the third interrupter will engage the ringing segment of the third interrupter, etc. Thus, when the interrupters have made one complete revolution, the currents from the generators have been delivered to each ot the cord circuits, iii-st one, thenanother, then another, and so on. @t course, it must be remembered that the selective keys are depressed to effectively employ but one gener at or at a time, that is, when a selective key is depressed, the circuit is closed through the desired current generator and the associated interrnpter. Thus, it appears that any one oi the generators may be etlectively einployed tor any of the cord circuit groups, current, however, being adapted to be connected with but one group of cord circuits a t any time.

Having thus described in general the various arrangements and relations ot the mechanisms, l. will now proceed to describe the operation ot the system with reference to AFig. 1. For the purpose ot illustration l will assume the subscriber at sub-station .t to be 'the calling subscriber. When he removes his receiver troni the switchhook, a circuit is closed through the indicating relay (i, thereby attracting its armature 18 to cause the closure ot the local circuit through the line lamp l". The operator then inserts her answering plug 19 into one ot thy associated spring jacks connected with the calling line and actuates her listening key to cause contact. between the springs t5 and e? and 4st and 4G respectively. The operator-s telephonic apparatus t) is thereby connected across the line, and she may converse with the calling subscriber to ascertain the conw nection desired. Immediately upon 'the in` sertion ot the calling plug in the line jack. a circuit is closed through the cut-oidl rela)v 3 as follows :wtroni the negative side oit the battery, through conductor 71, conductor 72, winding 2 4., the sleeve strand ot the answer ing side of the cord circuit, through the plug sleeve contact and jack thimble, conductor 3 and througih the cut-oft relay winding` to the positive side ot the battery. The armaturesl :and Zthen Vleave their back contacts, and the winding 24 `beingalso energized, the war-mature isalso attractedragainst the tension f .thefspring 26. .This would :tend to allow the spring 2S `tomalre Contact with thespring 30, butrthese springs are held in a` disengaged.y position by :reason of*V the ener-y gization ofthe Winding23 which is included 1n .-a circuit as follows lfrom the negative sideofthe? battery S, through conductor 71,

cord. circuit conductor y73 winding o the-'subscriber at sub-station B1.

spring jack of the line 'leadin'g'to sub-staltion B1, vthereby closing a circuit through the :cut-oit relay 3 and the supervisory lrelay oo iory the callingside of the cord circuit` as i'ollows :-irom the negative side of battery S, through conductor 71, conductorf76, wind-` ing 33, conductor 77, sleeve strand ofthe calling side of the cord circuit, sleeve contact of thevplug, thimblef15, conductor`16, cut-oil' relay 3 and back to the positive side of the battery. The armatures' and Q are,` therefore, attracted'to leave their Vrespective bach contacts, and winding 33 is energized to Iattract its. armature 34 against the 4tension of :the spring I'lChe spring x41 Vwill then be allowed to -make Contact witlrthe spring 42,-since thewinding 82 of thearmature 40 `which controls the spring 41 is not energized. llt may be Astated in passing that the winding 32 is controlled by the position of.' the switchhook at the sub-station when the plug is inserted in the jack. 'The receiver' at the-substation B?, however, being atA this time on its hoolr, the circuit vthrough the winding 82 is not closed, and this winding remainsl unenergized. Since the springs 41 and 42 are thus allowed to come vinto contact, the ilocal circuit through -the supervisory lamp 43 is closed as follows :--from the positiveside offthebattery, through conductor v75, conductor 7 S, springs 42 and 41, supervisory lamp 43, yand conductor 71 to .the negative-side ofthe battery. Being thus 40, C011= vductor 7.4, conductor tothe vpositive pole" of the battery. Thus, 'thearmature 27 is held in .its attracted .position whereby the springs-.Qvand AStfare held disengaged, the localfcircuit through the signal 81, there-v :foi-e, being held open. "Suppose vfor the pur!` Ipose of illustrationtthat the subscriber atl sub-station '1X desiresto be connected with The oper rator inserts her 'calling plugQO into the 51, spring 49, conductor 80, winding 61 of thefrelay 60, conductor-81, conductor 71, and back to the negative side offthebattery. Thelocling. relay 60 is thus energized, and

arinature,as before stated, isso mechanically connected with the actuatingleys of' -tl-ie associated selective apparatus vthat upon energization, it locks any ikey which has been depressed until it is denergized. The ley Z1481 is, therefore, lockedA in its depressed position. lVhen lthe relay'GOf-isfthus energized, its armature 82 is attractedto interrupt the sleeve-strand of the lcord circuit and its armature `62is attracted to engage the contact (53. Thisclosesa circuit through the relay 54 and the associated interrupters d as `follows:-'from the positive pole of 'the battery, through int-errupter CZ, conductor 83, contact ($3, armature G2, conduc- 'tor 84, winding, conductor 85 and conduct-or 71, bach to the negative pole oftlie battery. Thus,'during the time that the in- -terrupter L7/4 closes `the circuit just traced., the 'relay 54 will be energized to attract its armatures and 57. When the armatures `and 57 are thus attracted, they engage `respectively the Vfront contacts 53 land 58. The armature 55 leaves the back contact to interrupt the tip strand of the cord circuit. The associated 4current generator for the cord Acircuit group under consideration is connected between the contacts and 58 through an associated interruptor 68 and a selective key. Thus, upon energization of therelay 54 and since the key Z481 is depressed at this time, as before stated, Va bridge will be closed through the current generator 671, the interruptor (Z681 and ykey Z481 `as follows:-from contact 53, through conductor S7, spring 50, contact 52, conduc- 'tor 88, interrupter (Z631, current generator' G71, conductor 59 to lcontact Therefore, when the relay 54 is energized, the selected current 'will be sent over the line with which the callingI plug has been connected. AvSince, as before stated, the signal bells at sub-station B1 only are responsive to current generator 671, the subscriber at sub-station B1 will he the only-signaled subscriber on theline The active segment offthe inter- 'rupter (ZG* is so relatively adjusted as -to position with the interruptei' Z681 that ininiediately upon the energization ot the relay 54, the bridged circuit through the signaling current generator will be closed. The active segment, howeyer, oit the interrupter (im is inade slightly longer than the ringing seginent of the interrupter (GS. The pui'- pose of this construction as follows: lll-'Then the active segn'ieiit ot' the interruptor ZM connects with conductor 83, the circuit through the relay Will be closed, thereby placing the plug cords in the ringing position. Ringingl seginent ('55) ot interrupter Z681 will at the saine .instant connect the ringing` current to the line. lit these seginents were ot the saine length, when interrupter (ZM opens the circuitto release relay 5a, the ringing current would also be cut ott' immediately by ringing segment 69. Upon deenergiz :tion ot relay 54, the tip strand is continued through armature 55 and contact S6, through contacts 37 and 39, Winding 32 ot the supervisory relay and through conductorsI T8 and 75 to the positive grounded side ot the battery, and as the sleeve side ot the cord circuit when connected with. the line.y has always connection through Winding 353 ot the supervisory relay and through conductor 7l With the negative side ot the battery, the entire charge which the condensers in the telephones and the lines have received Will pass through the supeiyisory winding 32, and as this Winding controls the contacts 4:1 and 4t2 included in the circuit tor relay G() which in turn controls the circuit through relay 54, the signaling Would be seriously interfered with. l't is, tliei'etoi'e,iiecessary to maintain the actuation ot relay 60 and relay 54- controlled thereby a sufficient length ot tinie to allow the discharge ot the line through the ground connection tor the signaling' current interrupters, and this is accomplished by inaking the active segment of the interrupter (ZM slightly longer than ringino` seginent (i9 ot the interrupter (Z681. Relay oil is energized and ringing current at the saine tiine applied to the cord conductors and connected lines. After the corresponding brush leaves the ringing segment ot the interrupt-ei' (1G81, the active segment ot the ii'iterrupter (ZM on account oit its greater length still engages its brush and inaintains closure ot the circuit 'tor relay 54 and the charge retained in the condensers and the .line is led to ground through the grounded segnient 'TO ot the interrupter (Z681. )ritter the corresponding brush leaves the active seginent ot the interrupter (Gt, the circuit tor relay 5st. is opened and the relay dcnergized to again complete the tip strand through the Winding lto ground. The

line and other circuits are, therefore, en-

tirely relieved ot static charges betere andv after application ot the ringing impulses g thereto. lt inust be understood, ot course, i

aeree@ that the 'foregoing explanation in regard 1.o

the relative disposition ot the active segineiits ot the interrupters om and d68] niay be applied to the interrupters t-lA and tt ot all the ringing divisions.

The ringing circuit to signal the suhscriber inay be traced as tollowsz--troin generator (ST1 through interruptor dot?, conductor 88, Contact 52, spring 50, conductor 8T, contact 523, arina'ture 55, tip strand oit the calling side ot the cord circuit, tip spring ot the spring jack 13', line liinb u. through condenser and signal bells at sul'i-siation l, back to the central station through line liinb b', sleeve spring ot the spring jack, sleeve contact et the plug, sleeve strand, a rinature 5T, contact 58, and conductor 5S) bach to the other pole ot the signal current generator (ST1. then the active segnient ot the interruptor d becomes disconnected troni conductor 82E, relay i-lbecoines cleenergir/.wt but on account ol the arrangement above described, the lines will be tree .troni .statul charge. The length ot such current llow tor the relay 5st iuust evidently be adjusted to correspond to the adjustment ot' the ringingl segnients ot the corresponding ringing current interiuliiters which have hereinbetore been described in detail. llpon receiving the signal.y the called subscriber remore-` his receiver troni the su'itchhool, therclny closing a circuit through winding 3Q as tollows troin the positire pole of the batteur. through conductor T5, conductor T8, winding 32, through a part oi: the tip strand. contacts 3) and 37, through another part et the tip strand, Contact tio, arniature :73, tip strand, tip contact oit the plug, tip spring ot the spring ack 3, line linih u, the switchhook and telephonie` apparatus at the suhstation, line liinb o', sleeve strand ot spring jack 153/, sleeve Contact oi the plug, .slcere strand, conductor TT, Winding El?) and conductor Tl to the negative pole et thel hattery. `Winding 3Q is thus energized, and the arinature -lO is attracted `whereby the springs -l-l and part contact. These contacts, as betere .st-ated, control the local circuit through the supervisory lauip -l-PB, and this lainp is, therefore, extinguished upon thil removal ot' the receiver troni the switchhooh at the called sub-station. its betere statedN the contacts -tl and ffl-2 also control the circuit through the locking relay (it), and when this circuit is opened by the reinoral ot tln receiver trein the hook at the called station, the locking relay is deiiergized, and on account of its inechanical connection with the selective apparatus releases the hey {Z4-SU. This immediately breaks connection between the ringing generator and the line, and the operator is notified by the extinction et the supervisory lainp lil that the called subscriber has answered.

The subscribers are now connected tor l l (l plug, sleeve strand, 1 through f condenser 113', tip of plug,tip stran'd,throughfarina- Utfiiife, contact*86,contacts'37 :and 39 and condenser 2l, tip of .answering plug, tipl .spring of springjack 13, linelimb a anch :back .to Athe V.telephonie apparatus -at sub-j ibstation A, curi-enti being supplied tothe line:

- the common batteryfS.

:lVhenlthe subscriber at substation A rc-v 'placesfhis receiverronlthehook, the circuit.V through vftheivinding '28 is'broken. Thus,

the armature 27 is Vpermitted to retract, since,

-asbefore stated, the Winding 24 is energized to attract theiarmature 25 .onfaccountiof con; tact between "the plug `sleeve contact Vand 4thimble 15. :This release of .the armature 27:,alloivsthe spring 28y to engage the spring` .'30, andthe circuit throughlthe supervisoryv vlamp 31. is closed. Similarly, when' the subscriber at sub-station B1 vhas replaced his .receiver onthe hook, *the circuit through;

:.30 winding- 3.2 of the supervisory relayitoi' the.l

calling side is opened. to allowL the armature =l=0 to vretract ivhereby the springsial and d2. .are brought .into engagement, "thus-closing' :the circuit through. supervisory .lamp

: ileingtherebyi notified that conversation has been completed, ift-he .operator removes the plugs-from the jacks'to 4restore theentireap- `paratus to Yits Vnormal condition. The cord --circuits may .also beprovi'ded.ivith. a busy` 40 test arrangement controlled by: the auxiliary l contact-s 91: and :92 ofv the operatoi's listening hey. Before-the calling plug is inserted in ythejack ofthe called line,.the operatoigin orderto test Whether or not theline is busy,

45 -iapplies the tip of the plug tothe jack thimlble and actuatesfheivlistening fkey. If the A line is busy, current ivill i'i o \v 4as `follows from the negative :pole of the battery, Athroughconductoiul and winding 33 of the u-supervisory relay-'connected Withthe busy cord circuit, through the sleeve contact, through the engaged thimble, vthrough Ithe tip `of the applied .testing plug, through the tip strand `of .the testing cord circuit,

55-through Iafrmatuif'e 55 l'and contact'SG of the -relay 54, through conta-cts 3T and 38, through conductor 93, through engaging test con- =tacts 92 `and `91, `through conductor 9-ll, `through the test YWinding A95, through conductor 96 and through conductors 7'8 l:and 7 to the positive pole of the battery. This will cause the usual clickinthe .opeiiatoi-s 'receiver, :andshe will bek notiied of.y the busy condition of the line. :If the line :is :not

busy, thisci'rcuitvivillnot bc closed 'through 'fthe -test winding, and-'the operator connects the calling plug With the jacket' the line to be called andithen proceeds. as herei-nbet'ore described.

The relative arra ngement' between the selective signaling apparatus and the cord cir- I-cuits as hereindescribed has been found to be very 'e'icient and capable of being oper- "ated 'with la minimum expense.

ltzisa desirable feature that small signal.- ing current generators maybe employed, and it is evident from the foregoing that with the 'cord `circuitsfat the-exchange v'arranged in ringingdivisions,=better -resultsfmay be obtainedt'l-ianby the employment of large ring- :ing currentgenerators tofmeet the demands fwhich may-beniade uponthein. WVith'the `arrangemeuts 'as described herein, the current isdistributed 'as'to-time, alla-inging dilvisions being supplied with the saine amount ment vbeingsuch asto positively distributev the current among: cord circuit groups -as to 'time 'to prevent `at vany timeran oveidemand upoir'the- 'current generators.

l do not Wish to be limited to the exact varrangement and 'relation of the parts herein shown, as changes -lmay bereadily made by those-skilled inthe-fart Without departing from the-spiritandscope of my invention.

il: claim as neivfand desire to secure by Letters vPatent z l. :In a telephone exchange system, the combination lwith a central exchange, ot' substations k'connected 'therewith through telephone'lines,-cord circuits at the central exchange, a 4source of rin-ging current at the central exchange, and'means whereby said ringing current source may be periodically connected with `each vof said cord circuits successively.

2. Ina 'telephone exchange system, the combination with a central exchange, of sub- Vstations connected therewitn through telephone lines, coid circuits at-the central exchange, .a source .ofringing current at the central exchange, and interrupter means -wherebysaidsource maybe periodically connected lwith each ofsaid cord circuits in regular successive order.

3. In ya telephone exchange system, the combination `Withfa central exchange, of substatioiis lconnected"therewith through 'telephone lines. cord circuits .at ythe central exchange, fa source of ringing current atthe central exchange, and means -ivhereby said ringing Acurrent source vmay be :effectively lOO connected with said cord circuits successivelyr at regular intervals.

Il. l'n a telephone exchange system, the combination with a central exchange, of substations connected therewith through telephone lines, cord circuits at the central exchange divided into ringing divisions, a source et ringing current at the cent "al ex'- change, and means whereby said ringing current source may be periodically connected with each of said ringing divisions in regular successive order.

5. ln a telephone exchange system, the combination with a central exchange, of substations connected therewith through telephone lines, a plurality of groups of cord circuits at the central exchange, a source of ringing current at the central exchange, and means whereby said ringing current source may be periodically connected with each of said cord circuit groups in regular succes-- sive order.

G. ln a telephone exchange system, the combination with a central exchange, of substations connected therewith through telephone lines, cord circuits at the central exchange arranged in a plurality of groups, a source oi ringing current at the central exchange adapted to be connected in parallel ot' all the cord circuits in a single group, and means whereby said ringing current source may be periodically connected with each ot said cord circuit groups in regular successive order.

7. ln a telephone exchange system, the combination with a central exchange, ot substations connected therewith through telephone lines, cord circuits at the central exchange arranged in a plurality ot ringing divisions, a source of ringing current at the central exchange, and means whereby said ringing current source may be periodically connected with each of said cord circuit ringing divisions in regular successive order.

8. ln a telephone exchange system, the combination with a central exchange, oll substations connected therewith through telephone lines, cord circuits at the central exchange arranged into ringing divisions, a source of current at the central exchange, an interrupter t'or each ot said cord circuit groups, and means for successively connecting said source ot current through each of said interrupters with the associated cord circuitgroup. l

9. ln a telephone exchange system, the combination with a central exchange, of substations connected therewith through telephone lines, cord circuits at the central exchange arranged into ringing divisions, a source et ringing current at the central exchange, and an. interrupter for each of said cord circuit groups through which said source ot current is adapted to be connected with its associated cord circuit ringing dicorea@ vision, said interrupters being so timed rela tive to each other that their active periods` follow each other in regular successive order.

l0. ln a telephone exchange system, the combination with a central exchange, oit substations connected therewith through telephone lines, cord circuits at the central exchange arranged into ringing divisions, a source ot' ringing current at the central exchange, an interrupter for each ot' said cord circuit ringing divisions whereby said source ot ringing current may be successively connected with each ot said cord circuit ringing divisions through its associated interrupter.

ll. ln a telephone exchange system, the combination with a central exchange, of substations connected therewith through telcphone lines, cord circuits at the central cx change arranged into ringing divisions, a source ot ringing current at the central ex change, an interrupter for each of said ringing divisions, said interrupters being so timed that their active periods follow one another in regular successive order, and switching apparatus whereby said source ot current may be connected with any ot said cord circuit ringing divisions through the associated iiiterrupter.

l2. ln a telephone exchange system, the combination with a central exchange, ot substations connected therewith through tele phone lines, cord circuits at the central exchange arranged into a plurality ot ringing divisions, a source of ringing current at thc central exchange, and an interrupter tor each of said ringing divisions through which said current source is adapted to be con nected with the associated ringing division. said interrupters being so timed that the active period of each interrupter begins immediately upon the cessation of the active period of another interrupter and is followed iimnediately upon its cessation by the active period et a succeeding interrupter.

13. ln a telephone exchange system, the combination with a central. exchange, of suhstations connected therewith through telephone lines, cord circuits at the central exchange a ranged into a plurality of ringing divisions, a source of ringing current` at the central exchange normally disconnected troni the cord circuit, interruljiters for said cord circuit divisions through which said source of current is adapted to be successively connected thereto, a relay controlling the connection of said source ot current with the cord circuit, and switch mechanism adapted upon actuation to energize said relay and to connect said source ot current through au interrupter with the contacts ot' said relay whereby said current source may be connected with the line.

11i. In a telephone exchange system, the combination with a central exchange, et substations connected therewith through telephone lines, cordcircuits at the. central exchangedivided-into alplurality of ringing divisions, a source of ringing 'current at the central exchange, an interrupter for each of said ringing divisions, a relay controlling the connection of said-source with the cord circuit, switch mechanism for each of said vringing divisions adapted uponactuation to connect'said source of current through the associated ringing current interrupter with the contacts of said relay, and interrupter means connected in the circuit otr said relay, said switch mechanism being adapted to close the circuit' through said relay, a source of current and'saidinterrupters whereby saidfre- Vlay is periodically energized, said ringing current interrupter being ad'apted to close the circuit through saidV source of ringing current while said relay is energized.

15. In a telephone exchange system, the combination with a central exchange, of substations connected therewith through telephone lines, cord circuits at the central exchange, a source of ringing current at the central exchange normally disconnected from the cord circuit, a relay controlling the connection of said source with the cord circuit, a second relay controlling the circuit :tor said first relay, and interrupter means for each oiI said cord circuits for periodically causing closure of said circuit to periodically cause action of the first relay to connect the source with the cord circuit.

16. In a telephone exchange system, the combination with a central exchange, of substations connected therewith through telephone lines, cord circuits at the central exchange divided into a plurality ot ringing divisons, a source of ringing current at the central exchange, a relay controlling the connection of said source of current to the cord circuit, interrupter means tor the circuit of said relay, switch mechanism for closing the circuit through said relay, one ot' said interrupters and a source of current, a ringing current interrupter for each of said divisions, said switch mechanism being adapted upon actuation to connect said ringing current source through the associated ringing current interrupter with the contacts of said relay, said ringing current source being adapted to be connected with the cord eircuit upon the periodical energization of said relay, said ringing current interrupter beingI so timed with reference to the associated relay circuit interrupter that said ringing circuit will be closed when said relay is energized to send ringing current over the line connected with said cord circuit.

17. In a telephone exchange system, the combination with a central exchange, of substations connected therewith through telephone lines, cord circuits at the central exchange arranged in a plurality of ringing divisions, a ringing current source at the central exchange, a relay for each cord circuit controllingthe-connection of said ringing source to the cordcircuit, an interrupter for each of said cord circuit divisions serially included'with the associated controlling relay andv a common source of current, switch mechanism adapted upon actuation to close the circuit through said controlling rela'y, the associated interrupter and the source of current, a ringing current intcrrupter tor each cord circuit division, said switch mechanism upon actuation being adapted to connectsaidringing current source with the con-` tacts of said controlling relay through said ringingk current interrupter, said ringing current:interrupter and said associated relay circuit interrupter being so relatively timed that said ringing current source will be connected with lthecord circuit and the line connected therewith when said relay is energized.

1S. In a telephone exchange system, the combination with a central exchange, ot substations connected therewith through telephone lines, cord circuits at the central exchange arranged into a plurality ot' ringing divisions, a source ot' ringing current at the central exchange normally disconnected trom the cord circuits, a relay controlling the connection otl said ringing current to the cord circuit, an interrupter for each ot the cord circuit divisions serially included in the controlling relay circuit, a common source of current, switch mechanism tor closing the circuit through said controlling relay, aid associated interrupter and sail common source ot current, a second relay controlling the circuit ot' the first relay, said switch mechanism being adapted upon actuation to energizesaid relay to continue the circuit through said first relay, said second relay also forming locking means whereby said switch mechanism is held in an actuated position, a ringing current interi-ruiter for each of said cord circuit divisions, said switch mechanism being adapted upon actuation to connect said source ot current with the contacts ot said first controlling relay` said relay circuit interrnpters being adapted to periodically energize the first controlling relay, said ringing current interrupters being so timed relative to the associated relay circuit interrupters that the ringing current will be connected with the line during such energized period.

1.9. ln a telephone exchange system, the combination with a central exchange, of substations connected therewith through telephone lines, cord circuits arranged in groups at the central exchange, a source ot ringing current, and interrupter means whereby said ringing current may be successively connected with each of said cord circuit groups.

20. In a telephone exchange system. the combination with a central exchange, ot substations connected therewith through telephone linee, cord circuits for interconnecting Suid telephone lines arranged in groups at the central exchange, a source of ringing current, und un interrupter between Said source ot' current and each cord circuit, Said interrupters beine` so tiined relzitivel)7 to each. other that Seid Source of current is periodically connected with each of saidcord circuit groupe in regular Successive order.

2l. ln a telephone exchange System, the combination with e central exchange, of substzitione connected therewith 'through telephone lines, interconnecting cord circuits ru-nged in groups at the central exchange, 2L Source of signaling current ut the central exchange, one liinb of each of S21-id cord circuits being adapted to be connected with one liinb of each of all the other cord circuits und with one terininul of Suid yeource of cur rent7 und an interrupter associated with en ch cord circuit group, one segment of cach interrupter being connected with the corre eponding Segment of all the other interruptere une with one terniinel ot euid Source oit current, the brush Contact ot Suid inter rupter being adapted to be connected with the other limb ot` the associated cord circuit` enid segments being so tin'ied that Suid source oif current will be periodically connected with euch ot' Suid cord circuit gro pe in rcguiur eucceeeive order.

ln Witness whereof, l hereunto `euhecribo in)T naine this fifth day of Jun. 'IL 190i".

MER NTT S. CUNYYNH. lVitneesee P. E. TUCKER, WILLIAM RAmfoRn. 

